Acid Pickling

The most common method of eliminating unwanted pigmented compounds that are mostly oxides of metal is by acid pickling. Either hydrochloric, diluted sulphuric or phosphoric acid is sprayed on the part or part is dipped into a tank, agitated and after that washed & rinsed thoroughly. Sometimes it is essential to add pickling inhibitors such as detergents, liquid glycol, either, etc. to reduce the action of acid upon the metal specifically aluminium and other non-ferrous metals.

Acid pickling is also utilized in the elimination of oil and grease. In some of applications, acid pickling is utilized to remove light rust. Acid cleaners alternatively are chemically limited in their ability to eliminate polishing and buffing compound. Soaps and other acid hydrolysable materials exist in these compounds are decomposed by acid cleaners into insoluble materials. This prevents the utilization of acid pickling in most instances.

Acid cleaning of steel parts make hydrogen that is absorbed by the steel and causes “hydrogen embrittlement”. In the steel the hydrogen might be decreased by heating the parts after pickling. As splash and vapours from the acid solution corrode equipment & tanks, the maintenance cost is high & working conditions are diagreeable.